NAME
mblen
—
get number of bytes in a multibyte
character
LIBRARY
library “libc”
SYNOPSIS
#include
<stdlib.h>
int
mblen
(const
char *s, size_t
n);
DESCRIPTION
Themblen
()
function usually determines the number of bytes in a multibyte character
pointed to by s and returns it. This function shall only
examine max n bytes of the array beginning from s.
In state-dependent encodings, s
may point the special sequence bytes to change the shift-state. Although
such sequence bytes corresponds to no individual wide-character code, the
mblen
()
changes the own state by them and treats them as if they are a part of the
subsequent multibyte character.
Unlike mbrlen(3), the first n bytes pointed to by s need to form an entire multibyte character. Otherwise, this function causes an error.
mblen
()
is equivalent to the following call, except the internal state of the
mbtowc(3) function is not affected:
mbtowc(NULL, s, n);
Calling any other functions in
library “libc” never changes the
internal state of
mblen
(),
except for calling
setlocale(3) with the LC_CTYPE
category
changed to that of the current locale. Such
setlocale(3) calls cause the internal state of this function to be
indeterminate.
The behaviour of
mblen
() is
affected by the LC_CTYPE
category of the current
locale.
These are the special cases:
- s == NULL
mblen
() initializes its own internal state to an initial state, and determines whether the current encoding is state-dependent. This function returns 0 if the encoding is state-independent, otherwise non-zero.- n == 0
- In this case, the first n bytes of the array pointed
to by s never form a complete character. Thus,
mblen
() always fails.
RETURN VALUES
Normally, mblen
() returns:
- 0
- s points to a nul byte (‘\0’).
- positive
- The value returned is a number of bytes for the valid multibyte character
pointed to by s. There are no cases that this value
is greater than n or the value of the
MB_CUR_MAX
macro. - -1
- s points to an invalid or incomplete multibyte
character. The
mblen
() also sets errno to indicate the error.
When s is equal to
NULL
, the mblen
()
returns:
- 0
- The current encoding is state-independent.
- non-zero
- The current encoding is state-dependent.
ERRORS
mblen
() may cause an error in the
following case:
- [
EILSEQ
] - s points to an invalid or incomplete multibyte character.
SEE ALSO
STANDARDS
The mblen
() function conforms to
ANSI X3.159-1989
(“ANSI C89”).